1. Field of the Invention
This invention relates to a vibration damping material of asphalt cement and, more particularly, to a vibration damping material used in structural members, such as posts, beams, floors or a ceiling surface of a civil construction or a building to damp a vibration and a mechanical vibration or the like due to an earthquake, wind and/or a traffic.
2. PRIOR ART
Heretofore, various types of elastic and viscoelastic materials have been employed for damping of vibrations of a civil construction or a building.
Elastic materials, such as plates-shaped or block-shaped hard rubber, hard synthetic rubber, etc. have been used. These materials lack vibration damping performance due to excessively strong rubber elasticity. Since the rubber itself does not have adhesion properties, it is necessary to coat an adhesive over the rubber, or to adhere a plate or the like having adhesion function to a surface of the rubber to compose a construction material of two or more layers.
Silicone resin or polymer materials are considered as the viscoelastic substance. Since the silicone resin is expensive and slightly deteriorates in its damping performance, it is improper to be employed as the vibration damping material of a building. Polymer materials have some problems regarding its vibration damping performance, cost and workability (which needs to be sealed due to liquid).
Asphalt cement is widely employed as a vibration damping material due to its excellent stickiness, deformability and water tightness.
However, the asphalt cement itself has disadvantages, such as low adhesive properties at ambient temperatures, brittleness, easy cracks at low temperature, and large flowability, low elasticity and hard restoration after tension or compression thereof at high temperature.
There are jointing materials for a civil construction and a building in which rubber and filler are mixed with asphalt cement. Since the jointing materials have large rubber elasticity and less energy consumption amounts, they are improper as for vibration damping material.
There are also paving materials in which rubber is mixed with asphalt cement. The paving materials have disadvantages, such as excessively small rubber elasticity to have its bad vibration damping performance and a low softening point to flow when using in a vertical surface.
The largest reasons why the vibration damping material for satisfying the above-mentioned various properties cannot be obtained are (1) material itself does not have strong adhesion properties: (2) material does not have stable and high damping performance in a wide temperature range: and (3) material does not have high viscous shearing resistance (high deformability and preferable restoration) in its shearing deformation.
Thus, recently there have been employed (1) a heat fusion type sheet made of an asphalt cement, thermoplastic resin and inorganic filler, which is heat-fused and adhered to a surface to be coated at the time of working the sheet, and (2) a sheet or a panel having a structure of two or more layers in which viscoelastic asphalt cement filled with rubber are adhered to a thin plate made of aluminum or the like.
Therefore, it has been desired to develop a material which has strong adhesion properties, suitable viscoelastic property, tensile strength, flowability resistance at high temperatures, stickiness and moldability at low temperatures, stable and high damping performance and high viscous shearing resistance (high deformability and preferable restoration) in a wide temperature range.